Single-crystal and polycrystalline diamond erosion studies in Pilot-PSI

TitleSingle-crystal and polycrystalline diamond erosion studies in Pilot-PSI
Publication TypeJournal Article
Year of Publication2018
AuthorsD. Kogut, D. Aussems, N. Ning, K. Bystrov, A. Gicquel, J. Achard, O. Brinza, Y. Addab, C. Martin, C. Pardanaud, S. Khrapak, G. Cartry
JournalJournal of Nuclear Materials
Date Published03/2018

Diamond is a promising candidate for enhancing the negative-ion surface production in the ion sources for neutral injection in fusion reactors; hence evaluation of its reactivity towards hydrogen plasma is of high importance. Single crystal and polycrystalline diamond samples were exposed in Pilot-PSI with the D+ flux of (4‒7) 1024 m−2s−1 and the impact energy of 7–9 eV per deuteron at different surface temperatures; under such conditions physical sputtering is negligible, however chemical sputtering is important. Net chemical sputtering yield Y = 9.7 10−3 at/ion at 800 °C was precisely measured ex-situ using a protective platinum mask (5 × 10 × 2 μm) deposited beforehand on a single crystal followed by the post-mortem analysis using Transmission Electron Microscopy (TEM). The structural properties of the exposed diamond surface were analyzed by Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Gross chemical sputtering yields were determined in-situ by means of optical emission spectroscopy of the molecular CH A-X band for several surface temperatures. A bell-shaped dependence of the erosion yield versus temperature between 400 °C and 1200 °C was observed, with a maximum yield of ∼1.5 10−2 at/ion attained at 900 °C. The yields obtained for diamond are relatively high (0.5–1.5) 10−2 at/ion, comparable with those of graphite. XPS analysis shows amorphization of diamond surface within 1 nm depth, in a good agreement with molecular dynamics (MD) simulation. MD was also applied to study the hydrogen impact energy threshold for erosion of [100] diamond surface at different temperatures.





Alternate TitleJ. Nucl. Mater.

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